Protocols is like the interfaces in Java and C#.
The protocols defines the properties, methods, and types that would require other types to implement.
A protocol can be adopted or implemented by a type.
Adopting a protocol means that a type will implement the definition defined in the protocol.
To define a protocol, use the protocol keyword.
protocol Printer {
func print()
}
The code above created a new protocol named Printer,
which defined a function named print().
If you coded a class that you wanted to adopt this protocol, you would write the code as follows.
class aClass:Printer {
}
In the code above, we defined a class that adopted the Printer
protocol.
When you adopt a protocol, the protocol name goes after the class
name and a colon :.
If the class is also inheriting another class, you must list the protocol name after the parent class.
For instance, if aClass inherited
the Person class, you would need to use the code as follows.
protocol Printer {
func print()
}
class aClass:Printer {
func print() {
println("Implement print for aClass")
}
}
var obj = aClass()
obj.print()
When you use protocols to specify variables, you must include the getter and/or setter definitions.
protocol Printer {
func print()
var i:Int {get set}
}
class aClass:Person, Printer {
var i = 0
func print() {
println("Implement print for aClass & i = \(self.i)")
}
}
var obj = aClass()
obj.print()